Organic electronic devices employing semi-crystalline organic semiconducting polymers, e.g., poly(3-hexylthiophene) (P3HT), have great potential for low cost and large throughput production. Performance of these devices depends strongly on the morphologies of the constituting organic components whose optical and electrical on the morphologies of the constituting organic components whose optical and electrical properties rely on the degree of crystallinity. Small changes in the internal structures, i.e., packing/orientation of polymeric chains and morphologies on the nanometer scale, can have a large influence on device operation in organic electronic devices. Stabilizing these materials and morphologies without significantly changing their favorable properties, either to ensure long-term performance or for further processing of more complex device architectures, presents a significant challenge. One of the methods of solving this challenge is to crosslink the semiconducting polymers, locking in favorable morphologies and nanostructures. Polythiophenes are among the most commonly applied polymers in organic photovoltaic devices. In organic light-emitting diode (OLED)-based devices, many other organic molecules/polymers are more common
One previously demonstrated approach to stabilizing polythiophenes incorporates functional groups that crosslink through reaction with one another, e.g., oxetane groups. This necessitates a high concentration of functional monomer and alters the polymer structure, and thus the optical and electronic properties. Others have used more reactive cross-linkers that are less likely to impact structure but introduce species potentially detrimental to polymer properties. Two recent examples demonstrate UV crosslinking of polythiophenes with fluoroarylazide groups, which can act as electron traps, and alkyl halides, which introduce halide-functional byproducts. This group has successfully stabilized P3HT using a thermally-initiated peroxide crosslinking method in exploring experimental routes to patterning organic semiconductors, in which a large concentration of peroxides had to be applied leading to dilution of P3HT and thus decreased light absorption.